1. Field of the Invention
The invention relates to a toothbrush comprising a plastic brush body having a head, a neck and a handle, as well as bristle bundles fixed to the head.
2. Description of the Prior Art
Toothbrushes are mainly used for cleaning teeth and interdental spaces, but frequently also exert a massaging action on the gingiva or the marginal area thereof. These two sought effects of a toothbrush run counter to one another. Whereas the cleaning of the teeth requires a strong brushing action, particularly in order to remove plaque or free the interdental spaces from food residues, the massaging of the gingiva must take place with restraint to avoid injuries (lesions).
Further contrary demands result from the fact that the bundles or bristles must be stiff enough to penetrate adequately deep into the interdental spaces when pressed on the tooth surfaces, but the gingiva is particularly sensitive in the interdental space. In addition, in certain cases dental neck sensitivity problems arise.
It is known that the cleaning action of a toothbrush can be increased by the ends of the bundle not being in one plane and instead arranged in stepped manner (U.S. Pat. Nos. 5,446,940 and 5,419,001), so as to ensure that all the bristles are in cleaning engagement with the tooth surfaces and interdental spaces and also penetrate all depressions when brushing the masticatory surfaces. This leads to a very complicated bristle facing topography and the manufacture of such toothbrushes is expensive. They are completely unsuitable for massaging the gingiva, because only few bundles have an action when brushing.
In addition, toothbrushes with V-shaped bundles are known, as are those with bundles having the free ends of the bristles on a conical surface (DE 37 44 630). This in particular aids the penetration of the bundle tips in the interdental spaces, but at the same time the abrasion on the tooth and the dental neck and the injury risk on the gingiva (lesions) are increased. Knowing this disadvantage, in the known toothbrush only a centrally bristle bundle is made conical and also by means of a spring is mounted in a bore on the head of the brush body. Such a construction in no way satisfies modern hygienic requirements, because oral hygiene agent and other dirt residues are deposited in the bore. An effective cleaning of the toothbrush is impossible, so that after a short time the spring action is lost due to deposits.
It is finally known (EP 613 636) to make the neck of a toothbrush resilient, so as to avoid an excessive pressing force on the part of the bristles, namely independently of the contouring of the bristle bundle. At the same time it must be ensured that the bristle head gives way on reaching a given pressing force limit. The same aim is to be achieved in another toothbrush (DE 42 11 811) in that the head and neck of the toothbrush on the brush body are mounted about the longitudinal axis thereof and on exceeding the limit turn round the longitudinal axis, so that the bristles are disengaged. However, here again no account is taken of the effectiveness of cleaning and the massaging action.
The problem solved by the invention is the construction of a toothbrush so that in the case of a completely satisfactory cleaning action on all the tooth surfaces and in the interdental spaces, it is also possible to bring about a restrained massaging of the gingiva and avoid abrasions on the tooth and dental neck and lesions on the gingiva.
This solution is provided by a toothbrush comprising a plastic brush body having a head, a neck and a handle, as well as bristle bundles fixed to the head, in that the free ends of the bristles of at least part of the bundles are located on an approximately conical envelope surface with a cone angle .alpha.=30 to 90.degree. and the neck of the brush body in the case of an application force K-500 to 1200 grams acting on the bristles gives way in resilient manner, and the application force being the greater the smaller the cone angle .alpha. is.
On applying the toothbrush the longer bristles of the conical bristle bundles give way in the interdental spaces and clean the tooth surfaces facing each other, whereas the shorter bristles ensure an adequate cleaning of the outer and inner tooth surfaces respectively. In the case of the greater pressure the bundles give way. The bristles engaging with the tooth surfaces then have a scraping effect with their circumferential surface, whereas the reshaped bristles continue to act in the interdental spaces. In the case of an excessive application force the neck of the toothbrush resiliently gives way, so that the pressure on the teeth or gingiva cannot be further increased. This protects the teeth against abrasions and the gingiva against injuries.
The spring tension of the neck is chosen as a function of the desired cone angle of the bristle bundles in such a way that the neck gives way all the more the greater the cone angle is. Therefore the cone angle and pressing force have an approximately inversely proportional relationship.
Preferably the bristle bundles have a cone angle between 50 and 70.degree. and the neck is so designed that it gives way with an application force between 700 and 900 grams.
The application force can be set in different ways, e.g. by a corresponding configuration of the cross-section of the neck and consequently its moment of inertia. The bending strength of the neck can be influenced by the nature of the plastic. It is also possible to position, e.g. insert or integrate a spring on the neck. These measures can naturally also be combined. It is also possible to adjust the application force to the physiological requirements of the user, e.g. the force will be made lower for children than for adults. In the same way account will be taken of users having sensitive or less sensitive dental necks or gums.
In all cases the free ends of the bristle should be spherically and preferably hemispherically rounded.
The action of the bundles can also be influenced by their cross-section. For example, the bundles can have a circular, oval or polygonal cross-section.
In the same way the cleaning action can be influenced by a different stiffness or hardness of the bristles of an individual bundle or one bundle compared with the others.
It is finally advantageous if the bundles are located on a carrier or support, which is interchangeably fixed to the head, so that in the case of wear only the carrier or support with the bundles has to be replaced, which leads to an environmentally protecting construction.
Another preferred construction is characterized in that the head tapers conically or in wedge-shaped manner towards its free end, so that in particular confined or difficultly accessible areas in the oral cavity can be reached.